Circuit-design supporting apparatus, circuit-design supporting method, computer product, and printed-circuit-board manufacturing method

ABSTRACT

An FPGA-information managing unit included in a circuit-designing CAD apparatus retrieves FPGA information, such as pin assignment information and attribute information, that is created by an FPGA-designing CAD apparatus. A library creating unit creates a symbol library by using the FPGA information. When creating a symbol library, if an FPGA subjected to create the symbol library is arranged in the circuit diagram, the library creating unit manages not to change a portion dividing and a pin layout of the existing symbol library arranged in the circuit diagram as much as possible. When arranging a symbol of the FPGA that a symbol library is newly created, a circuit-diagram reflecting unit arranges the symbol without changing the existing layout.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technology for supporting (aiding)designing a circuit in which a Programmable Logic Device (PLD) is usedas a component.

2. Description of the Related Art

In a circuit design CAD, when a PLD such as an FPGA (Field ProgrammableGate Array) is used as a component, a circuit designer needs to create asymbol of the PLD after designing the PLD and register the symbol in asymbol library. However, the circuit designer's main practice is todesign a circuit by coordinating components, so that most of circuitdesigners are unused to create a symbol of a component. Therefore, tocreate a symbol each time upon a design change of the PLD imposes aheavy burden on the circuit designer.

Consequently, there has been developed a technology for supporting acreation of a symbol of the PLD. For example, Japanese PatentApplication No. Laid-open No. 2006-79447 discloses an FPGA designsupporting apparatus that automatically creates an FPGA library based oninformation on a pin layout of an FPGA.

However, there is a problem such that the FPGA library is created by theFPGA design supporting apparatus, though, an FPGA symbol in the circuitdiagram needs to be replaced each time the FPGA is changed duringdesigning the circuit. Furthermore, in the FPGA symbol created by theFPGA design supporting apparatus, a portion dividing and a pin layoutare changed due to a change of the FPGA in most cases, and thus it maybe necessary to change the circuit diagram drastically.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partially solve theproblems in the conventional technology.

According to an aspect of the present invention, a circuit-designsupporting apparatus that supports designing a circuit in which a PLD isused as a component includes a PLD-information receiving unit thatreceives PLD information, which is design information created by using aPLD-designing CAD with respect to the PLD; and a library creating unitthat creates a symbol library of the PLD to be used in a circuit designby using the PLD information.

According to another aspect of the present invention, a method forsupporting designing a circuit in which a PLD is used as a componentincludes receiving PLD information, which is design information createdby using a PLD-designing CAD with respect to the PLD; and creating asymbol library of the PLD to be used in a circuit design by using thePLD information.

According to still another aspect of the present invention, a method ofmanufacturing a printed circuit board, the method being employed by acircuit-design supporting apparatus that supports designing a circuit inwhich a PLD is used as a component includes receiving PLD information,which is design information created by using a PLD-designing CAD withrespect to the PLD; and creating a symbol library of the PLD to be usedin a circuit design by using the PLD information.

According to still another aspect of the present invention, acomputer-readable recording medium stores therein a computer programthat causes a computer to implement the above methods.

The above and other objects, features, advantages and technical andindustrial significance of this invention will be better understood byreading the following detailed description of presently preferredembodiments of the invention, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram for explaining a concept of an FPGAcoordinated design according to a first embodiment of the presentinvention;

FIG. 2 is a functional block diagram of the FPGA coordinated designsystem according to the first embodiment;

FIG. 3 is an explanatory diagram for explaining circuit designing;

FIGS. 4A and 4B are explanatory diagrams for explaining a symbol libraryof an FPGA;

FIG. 5 is a diagram of an example of FPGA information stored in anFPGA-information storing unit;

FIG. 6 is a diagram of an example of a symbol library stored in asymbol-library storing unit;

FIG. 7 is a diagram of an example of a pin swap;

FIG. 8 is a diagram of an example of how a pin swap is reflected in acircuit diagram;

FIG. 9 is a diagram of an example of a constrained condition stored in aconstrained-condition storing unit;

FIG. 10 is a diagram of an example of a change history stored in achange-history storing unit;

FIG. 11 is a diagram of an example of notification information that isoutput to an FPGA-designing CAD apparatus by a history output unit;

FIG. 12 is a diagram of an output format of the notificationinformation;

FIG. 13 is a flowchart of a process for creating a symbol library and aprocess for arranging a symbol, which are performed by acircuit-designing CAD apparatus;

FIG. 14 is a flowchart of a process for checking an input/outputattribute, which is performed by a DRC unit;

FIG. 15 is a flowchart of a process for checking a differential signal,which is performed by the DRC unit;

FIG. 16 is a flowchart of a process of checking a power supply voltage,which is performed by the DRC unit;

FIG. 17 is a flowchart of a process for pin swapping, which is performedby a pin-swap processing unit;

FIG. 18 is a flowchart of a process for outputting a change history,which is performed by the history output unit;

FIG. 19 is an explanatory diagram for explaining the concept of an FPGAcoordinated design according to a second embodiment of the presentinvention;

FIG. 20 is a functional block diagram of an FPGA coordinated designsystem according to the second embodiment;

FIG. 21 is a diagram of an example of a net list retrieved by a net-listretrieving unit;

FIG. 22 is a diagram of an example of a net list output by a net-listconverting unit;

FIG. 23 is a diagram of an example of a temporary library created by atemporary-library creating unit;

FIG. 24 is a flowchart of a process for outputting information for apackage-designing CAD, which is performed by a temporary-librarycreating apparatus;

FIG. 25 is a flowchart of a process for reflecting a considerationresult of a package, which is performed by the temporary-librarycreating apparatus; and

FIG. 26 is a functional block diagram of a computer that performs acircuit-designing CAD program according to the first embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments according to the invention are explained in detailbelow with reference to the accompanying drawings. Incidentally, a casein which the present invention is applied to an FPGA is mainly explainedin the embodiments.

First, a concept of an FPGA coordinated design according to a firstembodiment of the present invention is explained. FIG. 1 is anexplanatory diagram for explaining the concept of the FPGA coordinateddesign according to the first embodiment. As shown in the drawing, inthe FPGA coordinated design according to the first embodiment, anFPGA-designing CAD apparatus 10 that supports an FPGA design, apackage-designing CAD apparatus 20 that supports a package design of aprinted circuit board, and a circuit-designing CAD apparatus 100 as acircuit design supporting apparatus that supports a circuit designcooperate with one another to support a designer.

Specifically, the circuit-designing CAD apparatus 100 receives FPGAinformation such as a pin layout that is created by the FPGA-designingCAD apparatus 10, and creates a symbol library. When creating a symbollibrary of an FPGA, if the FPGA subjected to create a symbol library isarranged in a circuit diagram, i.e., if a symbol library is newlycreated due to a change in the FPGA, the circuit-designing CAD apparatus100 creates a symbol library by using information on the existingsymbol, such as a portion assignment and a layout of a symbol pin, asmuch as possible.

As described above, the circuit-designing CAD apparatus 100 creates thesymbol library of the FPGA by using the FPGA information, so that acircuit designer needs not create the symbol library of the FPGA.Therefore, workloads of the circuit designer can be reduced. Also, whena symbol library is newly created due to a change of the FPGA, thecircuit-designing CAD apparatus 100 creates a symbol library by usinginformation on the existing symbol as much as possible. Therefore, it ispossible to reduce modifications of the circuit diagram, and thus anefficiency of the circuit design can be improved.

Furthermore, when a DRC (design rule check) is performed, thecircuit-designing CAD apparatus 100 performs the DRC by referring to theFPGA information such as a pin input/output attribute that is created bythe FPGA-designing CAD apparatus 10. For example, the circuit-designingCAD apparatus 100 checks the number of output pins by referring to thepin input/output attribute of the FPGA with respect to each of nets. Inthis manner, the circuit-designing CAD apparatus 100 performs the DRC byreferring to the FPGA information such as the pin input/outputattribute, and thus the DRC can be performed more precisely.

Furthermore, when a pin swap occurs in a package design, thecircuit-designing CAD apparatus 100 retrieves pin swap information fromthe package-designing CAD apparatus 20, and reflects the pin swap in thesymbol library, the circuit diagram, and the like. In addition, thecircuit-designing CAD apparatus 100 reflects the pin swap in the packagedesign in a constrained condition such as a length of a line betweenpins. In this manner, the circuit-designing CAD apparatus 100 alsoreflects the pin swap in the package design in the constrainedcondition, and thus it is possible to eliminate an inconsistency ofcircuit design information and package design information.

Furthermore, the circuit-designing CAD apparatus 100 records a historyof the pin swap in the package design, and provides the historyinformation of the pin swap to the FPGA-designing CAD apparatus 10. Inthis manner, the circuit-designing CAD apparatus 100 records the historyof the pin swap in the package design, and provides the historyinformation of the pin swap to the FPGA-designing CAD apparatus 10, andthus it is possible to ensure a consistency among the FPGA design, thecircuit design, and the package design.

Subsequently, a configuration of an FPGA coordinated design systemaccording to the first embodiment is explained. FIG. 2 is a functionalblock diagram of the FPGA coordinated design system according to thefirst embodiment. As shown in the drawing, the FPGA coordinated designsystem includes the FPGA-designing CAD apparatus 10, thepackage-designing CAD apparatus 20, and the circuit-designing CADapparatus 100.

The circuit-designing CAD apparatus 100 supports a circuit design inwhich an FPGA is used as a component in cooperation with theFPGA-designing CAD apparatus 10 and the package-designing CAD apparatus20. FIG. 3 is an explanatory diagram for explaining the circuit design.As shown in the drawing, the circuit designer arranges a symbol, whichis registered as a symbol library associated with a component, in acircuit diagram, and connects symbol pins to each other, therebydesigning the circuit.

In a case of the FPGA, however, if a symbol is registered as a symbollibrary before a program is written thereon, pins are defined asinput/output pins because the pins can be used for either an input or anoutput. Therefore, when the registered symbol library is used, a pinused for an input is located on the right, conversely, a pin used for anoutput is located on the left, or buses are not arranged sequentially asshown in FIG. 4A, and thus the circuit diagram is complicated.

Therefore, it is necessary to create a symbol library each time aprogram is written. Consequently, in this case, the circuit-designingCAD apparatus 100 creates a symbol library of the FPGA each time aprogram is written. By creating a symbol library of the FPGA each time aprogram is written, as shown in FIG. 4B, pins used for an input can bearranged on the left, and also buses can be arranged sequentially.

To return to the explanation of FIG. 2, the circuit-designing CADapparatus 100 includes an FPGA-information managing unit 110, anFPGA-information storing unit 115, a library creating unit 120, asymbol-library storing unit 125, a circuit-diagram reflecting unit 130,a circuit-diagram storing unit 135, a DRC unit 140, a pin-swapprocessing unit 150, a constrained-condition storing unit 155, a historyoutput unit 160, and a change-history storing unit 165.

The FPGA-information managing unit 110 is a processing unit for managingFPGA information. The FPGA-information managing unit 110 retrieves FPGAinformation, such as a correspondence between a physical pin and alogical pin, a pin input/output attribute, a voltage value, and a banknumber, from a file output by the FPGA-designing CAD apparatus 10, andstores the retrieved FPGA information in the FPGA-information storingunit 115.

In such a case, after the FPGA-information managing unit 110 firststores the FPGA information in the FPGA-information storing unit 115,when the FPGA-information managing unit 110 retrieves FPGA informationand stores anew the retrieved FPGA information in the FPGA-informationstoring unit 115, the FPGA-information managing unit 110 further storesa change history indicating a change of the FPGA-information in thechange-history storing unit 165.

The FPGA-information storing unit 115 is a storing unit that storestherein FPGA-information under the control of the FPGA-informationmanaging unit 110. FIG. 5 is a diagram of an example of FPGA informationstored in the FPGA-information storing unit 115. As shown in thedrawing, the FPGA-information storing unit 115 stores therein a physicalpin name, a logical pin name, an input/output attribute, a bank number,a swap-group number, a differential attribute, and a power supplyvoltage with respect to each of pins.

The library creating unit 120 is a processing unit for creating a symbollibrary of the FPGA by using the FPGA information stored in theFPGA-information storing unit 115, and stores the created symbol libraryin the symbol-library storing unit 125. The library creating unit 120includes a portion dividing unit 121 and a symbol creating unit 122. Theportion dividing unit 121 divides the circuit diagram into portions. Thesymbol creating unit 122 creates a symbol of each of the portionsdivided by the portion dividing unit 121.

The portion dividing unit 121 divides the circuit diagram into portionsbased on a portion dividing rule that is specified by a user via a GUI.As the portion dividing, the circuit diagram are divided into theportions by each bank number, each bank group, each logical pin name, orthe like. Furthermore, the portion dividing unit 121 determinespositions of the rightmost pin and the leftmost pin on a symbol based oninput/output attributes, and determines the order of pins by sorting byattributes of the pins. Furthermore, the portion dividing unit 121receives a specification for displacing a pin between portions from theuser via the GUI, and displaces the pin.

Furthermore, when creating a symbol library, the library creating unit120 checks whether a symbol of the FPGA subjected to create the symbolis arranged in the circuit diagram. If the symbol is arranged in thecircuit diagram, the library creating unit 120 creates a symbol libraryby referring to information on the arranged symbol.

Specifically, the library creating unit 120 performs a portionassignment by referring a logical pin name as a key to the existingsymbol library. Furthermore, the library creating unit 120 creates asymbol library in which a symbol pin is arranged in the same position asa position where a previous pin is located in the existing symbollibrary. Namely, the library creating unit 120 assigns a pin having alogical pin name, which is included in the existing symbol, to the sameposition of the same portion as a position where a previous pin islocated in the existing portion, and assigns a pin having a logical pinname, which is not included in the existing symbol, to the same portionas a portion where a previous pin having the same physical pin name islocated. Furthermore, the library creating unit 120 arranges a pinhaving a logical pin name, which is not identical to that is used in theexisting symbol, in an unoccupied position on the symbol library. Ifthere is no unoccupied position on the symbol library, the librarycreating unit 120 extends a size of the symbol library in a downwarddirection, and arranges the pin in the extended position.

When a symbol of the FPGA subjected to create the symbol is arranged inthe circuit diagram, the library creating unit 120 creates a symbollibrary by referring to the information on the arranged symbol, and thusit is possible to minimize modifications of the circuit diagram due to achange of the FPGA design.

The symbol-library storing unit 125 is a storing unit that storestherein a symbol library of the FPGA. FIG. 6 is a diagram of an exampleof a symbol library stored in the symbol-library storing unit 125. Asshown in the drawing, the symbol-library storing unit 125 stores thereininformation on a library name, a date/time of creation, a version, anoccupied area, the number of figure tables, and the number of symbolpins, information on each of figures forming a symbol, and informationon each of pins.

The circuit-diagram reflecting unit 130 is a processing unit thatreplaces, if a symbol of the FPGA in which the symbol library is createdby the library creating unit 120 is arranged in the circuit diagram, thearranged symbol with a newly-created symbol. If a line is connected to apin having a logical pin name different from a previous logical pin namewhich is used before the replacement, the circuit-diagram reflectingunit 130 cuts off the line.

If a line is connected to a pin having a logical pin name different froma previous logical pin name which is used before the replacement, thecircuit-diagram reflecting unit 130 cuts off the line, and thus it ispossible to reduce missing a modification of the circuit diagram due toa change of the FPGA design.

The circuit-diagram storing unit 135 is a storing unit that storestherein information on the circuit diagram in which components arearranged. The circuit-diagram storing unit 135 is updated by thecircuit-diagram reflecting unit 130, if a symbol of the FPGA in whichthe symbol library is created by the library creating unit 120 isarranged in the circuit diagram.

The DRC unit 140 is a processing unit that performs a DRC. The DRC unit140 performs a DRC by referring to the FPGA information managed by theFPGA-information managing unit 110 in addition to information stored ina component library 30. Specifically, the DRC unit 140 checks aninput/output attribute, a differential signal, a power supply voltage,and the like. The DRC unit 140 performs the DRC by referring to the FPGAinformation, and thus the DRC associated with the FPGA can be performedprecisely.

The pin-swap processing unit 150 is a processing unit that receives pinswap information output by the package-designing CAD apparatus 20, andreflects the pin swap performed in the package design in the FPGAinformation, the symbol library, and the circuit diagram. In the FPGA,an operation inside the components can be changed by writing on aprogram, so that a pin replacement (a pin swap) of FPGA components isperformed in a phase of the package design to make the pin assignmenteasily. Therefore, the pin-swap processing unit 150 performs a processof reflecting the pin swap in the package design in the circuit design.

FIG. 7 is a diagram of an example of a pin swap. As shown in thedrawing, when lines connecting between the FPGA and other component arecrossed, the crossing of the lines can be eliminated by the pin swap ofthe FPGA. FIG. 8 is a diagram of an example of how a pin swap isreflected in the circuit diagram. As shown in the drawing, in thecircuit diagram, a pin layout is changed in symbols that respectivelyhave a physical pin name “D1”, “E1”, “F1”, and “G1”.

The pin-swap processing unit 150 further reflects the pin swap in thepackage design in a constrained condition such as a length of a linedistance between pins. The pin-swap processing unit 150 further reflectsthe pin swap in the package design in the constrained condition, andthus it is possible to ensure a consistency of design informationbetween the circuit design and the package design.

Furthermore, the pin-swap processing unit 150 instructs theFPGA-information managing unit 110 to store a change history of the FPGAinformation due to the pin swap. Then, the FPGA-information managingunit 110 stores the change history in the change-history storing unit165.

The constrained-condition storing unit 155 is a storing unit that storestherein a constrained condition relating to the circuit design, such asa length of a line between pins. FIG. 9 is a diagram of an example of aconstrained condition stored in the constrained-condition storing unit155. As shown in the drawing, the constrained-condition storing unit 155stores therein a constrained condition relating to a length of a linedistance between pins. For example, there is stored as a constrainedcondition that a length of a line between a pin having a physical pinname “G1” of a component “IC1” and a pin having a physical pin name “2”of a component “I12” is 50 mm or below.

The history output unit 160 is a processing unit that outputs a changehistory of the FPGA information, which is changed in the process ofreflecting the pin swap performed by the pin-swap processing unit 150,as notification information to a file in a form capable of inputting tothe FPGA-designing CAD apparatus 10.

The change-history storing unit 165 is a storing unit that storestherein a change history of the FPGA information, and managed by theFPGA-information managing unit 110. FIG. 10 is a diagram of an exampleof a change history stored in the change-history storing unit 165. Asshown in the drawing, the change-history storing unit 165 stores thereinchanged information on a date/time of processing and a swapped pin eachtime a process of pin swapping is performed. Furthermore, thechange-history storing unit 165 stores therein a date/time of processingeach time the history output unit 160 outputs a change history and alsoeach time the FPGA-information managing unit 110 retrieves FPGAinformation from the FPGA-designing CAD apparatus 10.

FIG. 11 is a diagram of an example of notification information that isoutput to the FPGA-designing CAD apparatus 10 by the history output unit160. As shown in the drawing, the history output unit 160 outputs aphysical pin name and a changed logical pin name after a pin swap, asnotification information, with respect to each of swapped pins. FIG. 12is a diagram of an output format of the notification information.

In this manner, the change-history storing unit 165 stores therein achange history of FPGA information, and the history output unit 160outputs the change history as notification information to a file in aform capable of inputting to the FPGA-designing CAD apparatus 10. Thus,it is possible to ensure a consistency of design information among thepackage design, the circuit design, and the FPGA design.

Subsequently, processing procedures of creating a symbol library and aprocess of arranging a symbol, which are performed by thecircuit-designing CAD apparatus 100, are explained. FIG. 13 is aflowchart of the processing procedures of creating a symbol library anda process of arranging a symbol, which are performed by thecircuit-designing CAD apparatus 100.

As shown in the drawing, in the circuit-designing CAD apparatus 100, theFPGA-information managing unit 110 retrieves FPGA information, such aspin assignment information and attribute information, from a file outputby the FPGA-designing CAD apparatus 10, and stores the retrieved FPGAinformation in the FPGA-information storing unit 115 (step S101).

Then, the library creating unit 120 determines whether a symbolcorresponding to the FPGA information retrieved by the FPGA-informationmanaging unit 110 is arranged in the circuit diagram (step S102). If thesymbol is not arranged in the circuit diagram, the library creating unit120 divides the circuit diagram into portions by using a portiondividing rule that is specified by the user (step S103), and determinesa position of a symbol pin in accordance with a predetermined rule forcreating a symbol, for example, by assigning pins to the right or leftbased on input/output attributes (step S104).

If the symbol is arranged in the circuit diagram, the library creatingunit 120 assigns a pin having the same logical pin name as that of aprevious pin to the same portion as a portion where the previous pin islocated by referring to the previously-performed portion assignment(step S105). If a pin has a logical pin name that is not used by aprevious pin, the library creating unit 120 assigns the pin to the sameportion as a portion where a previous pin having the same physical pinname is located (step S106). Then, the pin having the same logical pinname as that of the previous pin is arranged in the same position as aposition where the previous pin is located (step S107), and the pinhaving the logical pin name that is not used by the previous pin isarranged in an unoccupied position on the symbol (step S108).

The library creating unit 120 receives a specification for changing aportion assignment or a pin position from the user via the GUI. If thechanges are specified, the library creating unit 120 creates a symbollibrary by changing the portion assignment or the pin position (stepS109), and stores the created symbol library in the symbol-librarystoring unit 125 (step S110).

Then, the circuit-diagram reflecting unit 130 determines whether aprevious symbol of the FPGA in which the symbol library is created bythe library creating unit 120 is arranged in the circuit diagram (stepS111). If the previous symbol is arranged in the circuit diagram, thecircuit-diagram reflecting unit 130 replaces the arranged symbol with anewly-created symbol (step S112). If a line is connected to a pin to bearranged, which has a logical pin name different from a previous logicalpin name which is used before, the circuit-diagram reflecting unit 130cuts off the line (step S113).

Subsequently, the created symbol is arranged in the circuit diagram by acomponent input function that is specified by the user (step S114).

In this manner, if a symbol corresponding to FPGA information retrievedby the FPGA-information managing unit 110 is arranged in the circuitdiagram, the library creating unit 120 creates a symbol library byreferring to the previously-created symbol library, and thecircuit-diagram reflecting unit 130 replaces the arranged symbol with asymbol in which the symbol-library is newly created. Thus, it ispossible to minimize modifications of the circuit diagram due to achange of the FPGA design.

Incidentally, in this case, the library creating unit 120 refers to thepreviously-created symbol library, if an FPGA subjected to create asymbol library is arranged in the circuit diagram. Alternatively, thelibrary creating unit 120 can refer to the previously-created symbollibrary, if a symbol library of an FPGA subjected to create the symbollibrary is stored in the symbol-library storing unit 125.

Subsequently, a process for checking an input/output attribute, which isperformed by the DRC unit 140, is explained. FIG. 14 is a flowchart ofthe processing procedure of the process of checking an input/outputattribute, which is performed by the DRC unit 140.

As shown in the drawing, the DRC unit 140 focuses on any one of nets ina one-connection group, and obtains information on all pins included inthe focused net (step S201). Then, the DRC unit 140 focuses on any oneof the pins which information is obtained (step S202), and determineswhether the focused pin is for an FPGA component (step S203).

As a result, if the focused pin is for an FPGA component, aninput/output attribute of the pin is checked by referring to the FPGAinformation stored in the FPGA-information storing unit 115 (step S204).If the focused pin is not for an FPGA component, an input/outputattribute of the pin is checked by referring to the component library 30(step S205). Then, it is determined whether input/output attributes ofall the pins are checked (step S206). If there is any pin that is notchecked, the system control returns back to step S202, and a pin that isnot checked is focused to check its input/output attribute.

If input/output attributes of all the pins are checked, it is determinedwhether the focused net includes two or more output pins (step S207). Iftwo or more output pins are included, the user is informed about anerror indicating that the net is connected between the output pins (stepS208). Also, it is determined whether the focused net does not includeany output pin (step S209). If any output pin is not included, the useris informed about an error indicating that no output pin exists in thefocused net (step S210). If only one pin is an output pin, the user isinformed that the focused net is in a proper state (step S211).

Then, all the nets are determined whether the number of output pins ischecked (step S212). If there is any net that the number of output pinsis not checked, the system control returns back to step S201, and a netthat the number of output pins is not checked is focused to check thenumber of output pins. If all the nets are determined that the number ofoutput pins is checked, the process of checking an input/outputattribute is terminated.

In this manner, as for the FPGA component, the DRC unit 140 checksinput/output attributes of pins by referring to the FPGA information,and thus it is possible to precisely check input/output attributes inthe circuit including the FPGA.

Subsequently, a process for checking a differential signal, which isperformed by the DRC unit 140, is explained. FIG. 15 is a flowchart ofthe processing procedure of the process of checking a differentialsignal, which is performed by the DRC unit 140.

As shown in the drawing, the DRC unit 140 focuses on any one of nets,and obtains information on all pins included in the focused net (stepS301). Initial values of the number of positive pins, which denotes thenumber of pins which differential attribute is positive, and the numberof negative pins, which denotes the number of pins which differentialattribute is negative, are cleared to zero (step S302). Then, any one ofthe pins which information is obtained is focused (step S303), and it isdetermined whether the focused pin is for an FPGA component (step S304).

As a result, if the focused pin is for an FPGA component, a differentialattribute of the pin is checked by referring to the FPGA informationstored in the FPGA-information storing unit 115 (step S305). If thefocused pin is not for an FPGA component, a differential attribute ofthe pin is checked by referring to the component library 30 (step S306).Then, if the differential attribute is positive, the number of positivepins is incremented by “1”, or if the differential attribute isnegative, the number of negative pins is incremented by “1” (step S307).

It is determined whether differential attributes of all pins are checked(step S308). If there is any pin which differential attribute is notchecked, the system control returns back to step S303, and a pin whichdifferential attribute is not checked is focused to check itsdifferential attribute.

If differential attributes of all the pins are checked, it is determinedwhether the number of positive pins is a plus quantity and also thenumber of negative pins is a plus quantity, i.e., whether both a pinwith a positive attribute and a pin with a negative attribute exist inthe focused net (step S309). If the number of positive pins is a plusquantity and also the number of negative pins is a plus quantity, theuser is informed about an error indicating that a pin with a positiveattribute is connected to a pin with a negative attribute (step S310).If either one of the number of positive pins or the number of negativepins is a plus quantity, the user is informed that the focused net is ina proper state (step S311).

Then, all nets are determined whether a differential signal is checked(step S312). If there is any net that a differential signal is notchecked, the system control returns back to step S301, and a net that adifferential signal is not checked is focused to check its differentialsignal. If all nets are determined that differential signal is checked,the process of checking a differential signal is terminated.

In this manner, as for the FPGA component, the DRC unit 140 checksdifferential attributes of pins by referring to the FPGA information,and thus it is possible to precisely check a differential signal in thecircuit including the FPGA.

Subsequently, a process for checking a power supply voltage, which isperformed by the DRC unit 140, is explained. FIG. 16 is a flowchart ofthe processing procedure of the process of checking a power supplyvoltage, which is performed by the DRC unit 140.

As shown in the drawing, the DRC unit 140 focuses on any one ofcomponents (step S401), and further focuses on any one of pins includedin the focused component (step S402). Then, it is determined whether thefocused pin is a power supply pin (step S403). If the focused pin is nota power supply pin, the system control proceeds to step S410.

If the focused pin is a power supply pin, it is determined whether thefocused pin is for an FPGA component (step S404). If the focused pin isfor an FPGA component, a power supply voltage of the pin is checked byreferring to the FPGA information stored in the FPGA-information storingunit 115 (step S405). If the focused pin is not for an FPGA component, apower supply voltage of the pin is checked by referring to the componentlibrary 30 (step S406). Then, a voltage value of a net that the focusedpin is connected thereto is checked (step S407), and it is determinedwhether the voltage value is identical to the power supply voltage ofthe pin (step S408). If the voltage value is not identical to the powersupply voltage of the pin, the user is informed that the power supplyvoltage is not identical to the voltage value (step S409).

Then, it is determined whether all pins are checked (step S410). Ifthere is any pin that is not checked, the system control returns back tostep S402, and a pin that is not checked is focused to check a voltagevalue of the power supply pin.

If all the pins are checked, all the components are determined whether apower supply voltage is checked (step S411). If there is any componentwhich a power supply voltage is not checked, the system control returnsback to step S401, and a component which a power supply voltage is notchecked is focused to check a power supply voltage. If all thecomponents are determined that a power supply voltage is checked, theprocess of checking a power supply voltage is terminated.

In this manner, as for the FPGA component, the DRC unit 140 checks avoltage value of the power supply pin by referring to the FPGAinformation, and thus it is possible to precisely check a power supplyvoltage in the circuit including the FPGA.

Subsequently, a process for pin swapping, which is performed by thepin-swap processing unit 150, is explained. FIG. 17 is a flowchart ofthe processing procedure of the process of pin swapping, which isperformed by the pin-swap processing unit 150.

As shown in the drawing, the pin-swap processing unit 150 retrieves pinswap information that is created by the package-designing CAD apparatus20 (step S501), and replaces a physical pin name of a symbol library ofan FPGA in which a pin swap is performed (step S502).

Then, a logical pin name and an attribute relating to a logic, which areincluded in FPGA information of the FPGA in which the pin swap isperformed, are replaced (step S503), and a symbol in the circuit diagramis updated to the symbol in which the logical pin name and the attributerelating to the logic are replaced (step S504). As for a pin having aconstrained condition, the constrained condition is replaced each time apin swap is performed (step S505).

In this manner, as for a pin having a constrained condition, thepin-swap processing unit 150 replaces the constrained condition eachtime a pin swap is performed, and thus a pin swap in thepackage-designing CAD can be precisely reflected in information on thecircuit design.

Subsequently, a process for outputting a change history, which isperformed by the history output unit 160, is explained. FIG. 18 is aflowchart of the processing procedure of the process of outputting achange history, which is performed by the history output unit 160. Asshown in the drawing, after retrieving the latest FPGA information froma change history stored in the change-history storing unit 165, thehistory output unit 160 searches the last process of outputtingnotification information to be notified to the FPGA-designing CADapparatus 10 (step S601).

Then, pins subjected to perform a pin swap during from the last processof outputting notification information till now are marked (step S602).The latest attributes of the marked pins are output as notificationinformation to be notified to the FPGA-designing CAD apparatus 10 (stepS603).

Namely, after the FPGA-information managing unit 110 retrieves the FPGAinformation from the FPGA-designing CAD apparatus 10 and updates theFPGA information stored in the FPGA-information storing unit 115, thehistory output unit 160 outputs the latest attributes of the pinssubjected to perform a pin swap, which are not notified yet, asnotification information.

In this manner, the history output unit 160 outputs the latestattributes of pins subjected to perform a pin swap as notificationinformation to the FPGA-designing CAD apparatus 10 by using the changehistory stored in the change-history storing unit 165, and thus the pinswap in the package design can be reflected in the FPGA designinformation.

Furthermore, after the FPGA-information managing unit 110 retrieves theFPGA information from the FPGA-designing CAD apparatus 10 and updatesthe FPGA information stored in the FPGA-information storing unit 115,the latest attributes of pins only subjected to perform a pin swap,which are not notified yet, are output as notification information. As aresult, it is possible to avoid outputting wasted notificationinformation or overlapping notification information, and thus the pinswap in the package design can be efficiently reflected in the FPGAdesign information.

As described above, in the first embodiment, the FPGA-informationmanaging unit 110 included in the circuit-designing CAD apparatus 100retrieves FPGA information, such as pin assignment information andattribute information, which is created by the FPGA-designing CADapparatus 10, and the library creating unit 120 creates a symbol libraryby using the FPGA information. Therefore, the circuit designer needs notcreate the symbol library of the FPGA, and thus it is possible to reduceworkloads on the circuit designer.

Furthermore, at the time of creating a symbol library, if an FPGAsubjected to create a symbol library is arranged in the circuit diagram,the library creating unit 120 manages not to change a portion assignmentand a pin layout of the existing symbol library arranged in the circuitdiagram as much as possible. Also, when the circuit-diagram reflectingunit 130 arranges a symbol of an FPGA that a symbol library is newlycreated in the circuit diagram, the symbol is arranged without changingthe existing layout. Thus, it is possible to minimize modifications ofthe circuit diagram due to a change of the FPGA design.

Furthermore, in the first embodiment, when the DRC unit 140 included inthe circuit-designing CAD apparatus 100 performs a DRC, as for an FPGA,an attribute of a pin and the like are checked by referring to the FPGAinformation that is retrieved from the FPGA-designing CAD apparatus 10and stored in the FPGA-information storing unit 115 by theFPGA-information managing unit 110. Thus, it is possible to perform theDRC precisely.

Furthermore, in the first embodiment, the pin-swap processing unit 150included in the circuit-designing CAD apparatus 100 retrieves pin swapinformation from the package-designing CAD apparatus 20, and reflectsthe pin swap in the constrained condition in addition to the symbollibrary, the FPGA information, and the circuit diagram. Thus, it ispossible to eliminate an inconsistency of design information between thecircuit design and the package design.

Furthermore, in the first embodiment, the change-history storing unit165 included in the circuit-designing CAD apparatus 100 stores therein achange history of the FPGA information, and the history output unit 160outputs information for notifying the pin swap to the FPGA-designing CADapparatus 10 based on the change history stored in the change-historystoring unit 165. Thus, it is possible to ensure a consistency of designinformation among the package design, the circuit design, and the FPGAdesign.

In the first embodiment, a case has been considered in which a packagedesign of a printed circuit board is made based on a result of designinga circuit by using an FPGA component. To consider a desirable pinassignment for both the FPGA designer and the package designer inadvance contributes greatly to shortening a period of designing.Consequently, in a second embodiment of the present invention, there isexplained an FPGA coordinated design system that supports a coordinateddesign made between the FPGA designer and the package designer.

First, a concept of an FPGA coordinated design according to the secondembodiment is explained. FIG. 19 is an explanatory diagram forexplaining the concept of the FPGA coordinated design according to thesecond embodiment. As shown in the drawing, in the FPGA coordinateddesign according to the second embodiment, a temporary-library creatingapparatus 200 as a coordinated-design supporting apparatus receives FPGApin information, such as pin assignment information, which is created bythe FPGA-designing CAD apparatus 10, and creates a temporary library ofan FPGA. In this case, the temporary library denotes a component shapetype library that is required when the package-designing CAD apparatus20 performs a pin assignment, and is a temporarily-created library withrespect to the FPGA.

The temporary-library creating apparatus 200 retrieves pin swapinformation from the package-designing CAD apparatus 20, and reflectsthe retrieved pin swap information in FPGA information that is managedby its own self, and also notifies the pin swap information to theFPGA-designing CAD apparatus 10.

In this manner, in the second embodiment, the temporary-library creatingapparatus 200 receives the FPGA pin information that is created by theFPGA-designing CAD apparatus 10, and creates a temporary component shapetype library with respect to the FPGA. Thus, it is possible to considera pin assignment by using the package-designing CAD apparatus 20.

Subsequently, a configuration of the FPGA coordinated design systemaccording to the second embodiment is explained. FIG. 20 is a functionalblock diagram of the configuration of the FPGA coordinated design systemaccording to the second embodiment. As shown in the drawing, the FPGAcoordinated design system includes the FPGA-designing CAD apparatus 10,the package-designing CAD apparatus 20, and the temporary-librarycreating apparatus 200. The temporary-library creating apparatus 200includes a net-list retrieving unit 210, a net-list managing unit 220, anet-list converting unit 230, an FPGA-design-CAD interface unit 240, anFPGA-pin-information managing unit 250, a temporary-library creatingunit 260, and a pin-swap processing unit 270.

The net-list retrieving unit 210 is a processing unit that retrieves anet list created by the user and passes the net list to the net-listmanaging unit 220. FIG. 21 is a diagram of an example of a net listretrieved by the net-list retrieving unit 210.

As shown in the drawing, the net list includes a component defining unitthat defines a component and a net defining unit that defines a net. Inthe component defining unit, a component name and a component libraryname are described with respect to a component used for consideration.However, as for an FPGA component, there is no component library, sothat a module name (a name for distinguishing an FPGA) is describedfollowed by “FPGA/”.

In the net defining unit, a net name and a component pin connected tothe net are described with respect to each of nets. In this case, thecomponent pin is described in the form of “(a component name).(acomponent pin name)”.

Incidentally, as for an FPGA component, a logical pin name or a physicalpin name is described as a pin name (the physical pin name is markedwith “%”).

The net-list managing unit 220 is a managing unit that stores thereinand manages the net list retrieved by the net-list retrieving unit 210.Upon receiving a change of the net list input by the user via the GUI,the net-list managing unit 220 changes the net list.

The net-list converting unit 230 is a processing unit that converts thenet list managed by the net-list managing unit 220 into a format capableof inputting to the package-designing CAD apparatus 20. The net-listconverting unit 230 refers to FPGA information managed by theFPGA-pin-information managing unit 250 upon the conversion of the netlist.

FIG. 22 is a diagram of an example of a net list output by the net-listconverting unit 230. As shown in the drawing, the net list includes acomponent name, a library name, a component terminal number, a pin name,a net name, a swap group number, and a differential type with respect toeach of pins. In this case, the component terminal number is aconsecutive number assigned to each of pins.

The FPGA-design-CAD interface unit 240 is an interface to theFPGA-designing CAD apparatus 10. Specifically, the FPGA-design-CADinterface unit 240 retrieves FPGA pin information from theFPGA-designing CAD apparatus 10, and provides pin swap information tothe FPGA-designing CAD apparatus 10.

The FPGA-pin-information managing unit 250 is a managing unit thatstores therein and manages FPGA pin information retrieved by theFPGA-design-CAD interface unit 240. Furthermore, upon receiving aninstruction for changing a pin interval or FPGA pin information from theuser via the GUI, the FPGA-pin-information managing unit 250 changes theFPGA information.

The temporary-library creating unit 260 is a processing unit thatcreates a temporary library, i.e., a temporary component shape typelibrary by using FPGA pin information managed by theFPGA-pin-information managing unit 250 with respect to an FPGAcomponent.

FIG. 23 is a diagram of an example of a temporary library created by thetemporary-library creating unit 260. As shown in the drawing, in thetemporary library, there is described a land shape type library name, anX-coordinate, a Y-coordinate, an angle, and a pin name with respect toeach of pins. Incidentally, as for the land shape type library name,information stored in the FPGA-pin-information managing unit 250 uponreceiving an instruction from the user is used.

Furthermore, in the temporary library, an area denoting a size of acomponent is also described. Information on the area is used tocalculate a distance between components in designing the package design.Incidentally, a size of a component is calculated by thetemporary-library creating unit 260 based on a pin interval.

The temporary-library creating unit 260 creates a temporary librarybased on FPGA pin information, and thus it is possible to consider a pinassignment in the package-designing CAD.

The pin-swap processing unit 270 is a processing unit that retrieves pinswap information from the package-designing CAD apparatus 20 andinstructs the FPGA-pin-information managing unit 250 to change FPGA pininformation. The FPGA-pin-information managing unit 250 changes the FPGApin information, and also instructs the FPGA-design-CAD interface unit240 to notify the pin swap information to the FPGA-designing CADapparatus 10. Furthermore, the pin-swap processing unit 270 instructsthe net-list managing unit 220 to change a net list based on the pinswap information.

Subsequently, a process for outputting information for package-designingCAD, which is performed by the temporary-library creating apparatus 200,is explained. FIG. 24 is a flowchart of the processing procedure of theprocess of outputting information for package-designing CAD, which isperformed by the temporary-library creating apparatus 200.

As shown in the drawing, in the temporary-library creating apparatus200, the FPGA-design-CAD interface unit 240 retrieves pin assignmentinformation created by the FPGA-designing CAD apparatus 10 and passesthe pin assignment information to the FPGA-pin-information managing unit250, and then the FPGA-pin-information managing unit 250 creates FPGApin information (step S701).

Furthermore, the net-list retrieving unit 210 retrieves a net list (stepS702), and passes the net list to the net-list managing unit 220. Whenreceiving an instruction for changing the net list and the like from theuser, the net-list managing unit 220 changes the net list managed by itsown self. When receiving a specification of a pin interval and the likefrom the user (step S703), the FPGA-pin-information managing unit 250changes the FPGA pin information managed by its own self.

Then, the temporary-library creating unit 260 obtains coordinates of apin from the FPGA pin information and creates a temporary componentshape type library (step S704), and the net-list converting unit 230converts the net list (step S705). Then, the net-list converting unit230 outputs the converted net list to a file, and the temporary-librarycreating unit 260 outputs the created temporary library to the file(step S706).

In this manner, the temporary-library creating apparatus 200 creates thetemporary library, and thus it is possible to consider a pin assignmentby using the package-designing CAD apparatus 20. Furthermore, uponreceiving a specification of a pin interval and the like from the user,the FPGA-pin-information managing unit 250 changes the FPGA pininformation managed by its own self. Thus, the user can consider a pinassignment at various pin intervals.

Subsequently, a process for reflecting a consideration result of apackage, which is performed by the temporary-library creating apparatus200, is explained. FIG. 25 is a flowchart of the processing procedure ofthe process of reflecting a consideration result of a package, which isperformed by the temporary-library creating apparatus 200.

As shown in the drawing, in the temporary-library creating apparatus200, the pin-swap processing unit 270 retrieves pin swap information inthe package-designing CAD (step S801), and replaces a net including apin subjected to pin swap in the net list (step S802).

Then, the pin-swap processing unit 270 replaces a logical pin name and alogical attribute, which are included in FPGA information (step S803),and the FPGA-design-CAD interface unit 240 outputs information on thereplaced pin to a file (step S804).

In this manner, the pin-swap processing unit 270 retrieves the pin swapinformation in the package-designing CAD, and reflects the pin swap inthe net list and the FPGA pin information. And then, the FPGA-design-CADinterface unit 240 outputs information on the pin swap to the file.Thus, the pin swap in the package design can be reflected in the FPGAdesign information.

As described above, in the second embodiment, the FPGA-design-CADinterface unit 240 retrieves pin assignment information created by theFPGA-designing CAD apparatus 10, and the FPGA-pin-information managingunit 250 manages the pin assignment information retrieved by theFPGA-design-CAD interface unit 240 as FPGA pin information, and thetemporary-library creating unit 260 creates a temporary component shapetype library by using the FPGA pin information managed by theFPGA-pin-information managing unit 250 and outputs the temporarycomponent shape type library in the form capable of being read by thepackage-designing CAD apparatus 20 to the file. Thus, it is possible toconsider an early pin assignment by using the package-designing CADapparatus 20, and also to shorten a period of designing a printedcircuit board.

The circuit-designing CAD apparatus and the temporary-library creatingapparatus are respectively explained in the first and secondembodiments. Alternatively, it is also possible to achieve acircuit-designing CAD program and a temporary-library creating program,which respectively have the same function as the circuit-designing CADapparatus and the temporary-library creating apparatus, by realizingstructures of the circuit-designing CAD apparatus and thetemporary-library creating apparatus with software. Consequently, acomputer that performs the circuit-designing CAD program is explainedbelow. Incidentally, the temporary-library creating program can be alsoperformed by a similar computer.

FIG. 26 is a functional block diagram of a computer 300 that performsthe circuit-designing CAD program according to the first embodiment. Asshown in the drawing, the computer 300 includes a RAM 310, a CPU 320, anHDD 330, a LAN interface 340, an input/output interface 350, and a DVDdrive 360.

The RAM 310 is a memory that stores therein a computer program, anintermediate result of executing the computer program, and the like. TheCPU 320 is a central processing unit that reads a program from the RAM310 and performs the program. The HDD 330 is a disk device that storestherein a program and data. The LAN interface 340 is an interface forconnecting the computer 300 to other computers via a LAN. Theinput/output interface 350 is an interface for connecting the computer300 to an input device, such as a mouse or a keyboard, and a displaydevice. The DVD drive 366 is a device that reads/writes a DVD.

A circuit-designing CAD program 311 to be performed by the computer 300is stored in a DVD, and read out from the DVD by the DVD drive 360, andthen installed on the computer 300. Alternatively, the circuit-designingCAD program 311 is stored in, for example, a database of other computersystem that is connected to the computer 300 via the LAN interface 340,and read out from the database, and then installed on the computer 300.Then, the installed circuit-designing CAD program 311 is stored in theHDD 330, and read out by the RAM 310, and then performed by the CPU 320.

In the present embodiments, a case in which an FPGA is used as acomponent is explained. However, the present invention is not limited tothe above case. The present invention can also be applied to a case inwhich a PLD is generally used as a component.

According to an aspect of the invention, it is possible to create asymbol library by using information on a symbol arranged in a circuitdiagram. Thus, it is possible to reduce modifications of the circuitdiagram due to a design change of a PLD.

According to another aspect of the invention, when a design of the PLDarranged in the circuit diagram is changed, it is possible to reducechanges of the symbol. Thus, it is possible to reduce modifications ofthe circuit diagram due to a design change of the PLD, and therebyimproving an efficiency of designing a circuit.

According to still another aspect of the invention, when a design of thePLD arranged in the circuit diagram is changed, a circuit designer needsnot replace the symbol in the circuit diagram. Thus, it is possible toreduce modifications of the circuit diagram due to a design change ofthe PLD, and thereby improving an efficiency of designing a circuit.

According to still another aspect of the invention, it is possible toavoid missing a modification of the circuit diagram due to a designchange of the PLD. Thus, it is possible to improve a quality of thedesign.

Although the invention has been described with respect to a specificembodiment for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

1. A circuit-design supporting apparatus comprising: a PLD-informationreceiving unit that receives PLD information, which is designinformation created by using a PLD-designing CAD with respect to a PLD,wherein the PLD-designing CAD supports designing the PLD; and a librarycreating unit that creates a symbol library of the PLD in thecircuit-design supporting apparatus by using the PLD information, thecircuit-design supporting apparatus supporting designing a circuit of aprinted circuit board in which the PLD is used as a component, thelibrary creating unit determining whether an existing symbol of the PLDis arranged in a circuit diagram, and creating, if it is determined thatthe existing symbol is arranged in the circuit diagram, the symbollibrary based on information on an existing symbol library of theexisting symbol, changes from the existing symbol to a symbol whosesymbol library is created being fewest.
 2. The circuit-design supportingapparatus according to claim 1, wherein the library creating unitimplements a portion assignment, if it is determined that the existingsymbol is arranged in the circuit diagram, based on the information onthe existing symbol library of the existing symbol.
 3. Thecircuit-design supporting apparatus according to claim 2, wherein if itis determined that the existing symbol is arranged in the circuitdiagram, the library creating unit assigns a logical pin included in theexisting symbol arranged in the circuit diagram to a same portion as aportion where the existing symbol arranged in the circuit diagram islocated.
 4. The circuit-design supporting apparatus according to claim3, wherein if it is determined that the existing symbol is arranged inthe circuit diagram, the library creating unit arranges the logical pin,which is included in the existing symbol arranged in the circuitdiagram, in a same position as a position where the existing symbolarranged in the circuit diagram is located.
 5. The circuit-designsupporting apparatus according to claim 2, wherein if it is determinedthat the existing symbol is arranged in the circuit diagram, the librarycreating unit assigns a logical pin, which is not included in theexisting symbol arranged in the circuit diagram, to a portion based on aphysical pin name.
 6. The circuit-design supporting apparatus accordingto claim 5, wherein if it is determined that the existing symbol isarranged in the circuit diagram, the library creating unit arranges thelogical pin, which is not included in the existing symbol arranged inthe circuit diagram, in a position unoccupied by the existing symbolarranged in the circuit diagram.
 7. The circuit-design supportingapparatus according to claim 1, further comprising a change receivingunit that receives information relating to changes in the symbollibrary.
 8. The circuit-design supporting apparatus according to claim7, wherein the information relating to changes is information relatingto a portion assignment and a pin position.
 9. The circuit-designsupporting apparatus according to claim 1, further comprising a symbolreplacing unit that determines whether an existing symbol of the PLD isarranged in the circuit diagram, and if it is determined that theexisting symbol is arranged in the circuit diagram, replaces theexisting symbol arranged in the circuit diagram with the symbol forwhich the library creating unit created the symbol library.
 10. Thecircuit-design supporting apparatus according to claim 9, wherein if apin having a logical pin name different from that of the replaced symbolis connected to a line, the symbol replacing unit cuts off the line. 11.A method comprising: receiving PLD information, which is designinformation created by using a PLD-designing CAD with respect to a PLD,wherein the PLD-designing CAD supports designing the PLD; and creating,using a central processing unit of a computer that works as acircuit-design supporting apparatus, a symbol library of the PLD in thecircuit-design supporting apparatus by using the PLD information, thecircuit-design supporting apparatus supporting designing a circuit of aprinted circuit board in which the PLD is used as a component, thecreating including determining whether an existing symbol of the PLD isarranged in a circuit diagram, and creating, if it is determined thatthe existing symbol is arranged in the circuit diagram, the symbollibrary based on information on an existing symbol library of theexisting symbol, changes from the existing symbol to a symbol whosesymbol library is created being fewest.
 12. The method according toclaim 11, wherein the creating includes implementing portion assignment,if it is determined that the existing symbol is arranged in the circuitdiagram, based on the information on the existing symbol library of theexisting symbol.
 13. The method according to claim 12, furthercomprising replacing including determining whether the existing symbolof the PLD is arranged in the circuit diagram, and if it is determinedat the determining that the existing symbol is arranged in the circuitdiagram, replacing the existing symbol arranged in the circuit diagramwith the symbol for which the symbol library is created at the creating.14. A computer-readable recording medium that stores therein a computerprogram that causes a computer to work as a circuit-design supportingapparatus, the computer program causing the computer to execute:receiving PLD information, which is design information created by usinga PLD-designing CAD with respect to a PLD, wherein the PLD-designing CADsupports designing the PLD; and creating a symbol library of the PLD inthe circuit-design supporting apparatus by using the PLD information,the circuit-design supporting apparatus supporting designing a circuitof a printed circuit board in which the PLD is used as a component, thecreating including determining whether an existing symbol of the PLD isarranged in a circuit diagram, and creating, if it is determined thatthe existing symbol is arranged in the circuit diagram, the symbollibrary based on information on an existing symbol library of theexisting symbol, changes from the existing symbol to a symbol whosesymbol library is created being fewest.
 15. The computer-readablerecording medium according to claim 14, wherein the creating includesimplementing portion assignment, if it is determined that the existingsymbol is arranged in the circuit diagram, based on the information onthe existing symbol library of the existing symbol.
 16. Thecomputer-readable recording medium according to claim 14, furthercausing the computer to execute replacing including determining whetherthe existing symbol of the PLD is arranged in the circuit diagram, andif it is determined at the determining that the existing symbol isarranged in the circuit diagram, replacing the existing symbol arrangedin the circuit diagram with the symbol for which the symbol library iscreated at the creating.
 17. A method of manufacturing a printed circuitboard, the method being employed by a circuit-design supportingapparatus, the method comprising: receiving PLD information, which isdesign information created by using a PLD-designing CAD with respect toa PLD, wherein the PLD-designing CAD supports designing the PLD; andcreating, using a central processing unit of a computer that works asthe circuit-design supporting apparatus, a symbol library of the PLD inthe circuit-design supporting apparatus by using the PLD information,the circuit-design supporting apparatus supporting designing a circuitof a printed circuit board in which the PLD is used as a component, thecreating including determining whether an existing symbol of the PLD isarranged in a circuit diagram, and creating, if it is determined thatthe existing symbol is arranged in the circuit diagram, the symbollibrary based on information on an existing symbol library of theexisting symbol, changes from the existing symbol to a symbol whosesymbol library is created being fewest.